The invention relates to an electric lamp/reflector unit comprising:
a molded reflector body provided with a reflector portion having an optical axis, and with
an outer surface, and integrally with said outer surface a hollow neck-shaped portion around the optical axis; and
a concave reflecting inner surface between the neck-shaped portion and a light emission window transverse to the optical axis;
an electric lamp provided with a light-transmitting lamp vessel which is closed in a vacuumtight manner and has a cavity in which an electric element is arranged, and which has a first and a second end portion in mutual opposition, each with a seal through which a respective first and second current conductor connected to the electric element are passed from the lamp vessel to the exterior,
the second current conductor being guided through an opening in the reflector portion to the outer surface and being connected to a contact member provided on the outer surface,
while the electric lamp is fixed in the reflector body, with the first end portion in the neck-shaped portion, the cavity within the reflector portion, and the electric element on the optical axis.
Such an electric lamp/reflector unit is known from EP 595412. Units of this kind may be used for projection purposes, for example film or slide projection, but they may also be used in projection TV equipment. Users of such projection equipment continuously strive for miniaturization so as to render this projection equipment lighter in weight and more easy to use. It is a disadvantage of the known lamp/reflector unit that it has comparatively large dimensions, whereby further miniaturization of said projection equipment and/or the use of the lamp/reflector unit in comparatively small projection equipment is rendered difficult.
It is an object of the invention to provide an electric lamp/reflector unit of the kind described in the opening paragraph which has comparatively small dimensions, while at least substantially the same lumen output is obtained from the unit.
According to the invention, this object is achieved in that the electric lamp/reflector unit of the kind described in the opening paragraph is characterized in that a further contact member, to which the first current conductor is connected, is provided on the outer surface of the reflector body. The further contact member is not present in an axially displaced position behind the reflector portion, as in the known unit, but lies on the outer surface of the reflector portion. If the unit is projected along the optical axis onto a plane perpendicular to the optical axis, contours of the unit in said plane are imaged. The further contact member will lie within the contours of the reflector body upon such a projection. The contact members on the outer surface accordingly do not lead to an enlargement of the unit in radial direction, while nevertheless a reduction in size of the unit in axial direction is realized. The use of this unit in projection equipment of smaller dimensions has become possible as a result. The equipment in which the unit is to be mounted comprises a terminal for the electrical connection of the unit to the equipment. In the unit according to the invention, the terminal does not lie axially behind the unit, but next to the unit, this in contrast to the known unit. The terminal will lie within the contours of the reflector body upon projection along the optical axis. A smaller axial dimension of the equipment can thus be realized without leading to an increase in the radial dimension of this equipment. The equipment may thus be smaller and lighter. The lumen output of the unit according to the invention has remained at least substantially the same as that of the known unit. The unit according to the invention offers the advantage of a higher lumen output over a unit in which the smaller dimension of the unit is achieved in that the reflector portion was reduced in axial direction.
It is favorable when the contact members for the first and for the second current conductor are identical in shape. A smaller number of different operations are required as a result for achieving an electrical contact between the contact members and the current conductors. The operations are also less diverse, which simplifies the assembly of the unit. Moreover, a comparatively inexpensive assembling process can be achieved in the case of an automated manufacture on a large scale.
In a favorable embodiment, the first current conductor is passed from the first end portion through the neck-shaped portion to the exterior, where it is connected to the further contact member on the outer surface of the reflector portion. The two contact embers may then lie at a comparatively large distance from one another, so that the risk of flash-over between these members and/or current conductors is very small. It is then possible to operate or (re)ignite a discharge arc at a high voltage in a comparatively safe manner.
In an alternative embodiment, the electric lamp/reflector unit is provided with a starting aid. Preferably, the starting aid is connected to the further contact member provided on the outer surface via a connection conductor which is passed through a further opening in the reflector portion. The risk of start delays during (re)ignition of the lamp and hazardous situations arising therefrom is reduced by the starting aid.
In a favorable embodiment, the reflector body of the unit is manufactured from a glass-ceramic material which is resistant to thermal shocks. Glass-ceramic material has a comparatively small coefficient of thermal expansion, which is substantially zero in a temperature range from 20 to 500xc2x0 C. Such a glass-ceramic material is obtained through partial crystallization of glass. The use of the reflector body manufactured from such a material improves the thermal shock resistance of the reflector body. It was also found that the reflector body has a higher temperature resistance and is better resistant to a possible explosion of the lamp. The use of the reflector body at a comparatively high temperature, for example up to approximately 700xc2x0 C. instead of 450xc2x0 C. as in the case of a glass reflector body, has thus become possible, and the safety of the unit has been improved.
The neck-shaped portion renders it possible to secure the lamp vessel therein circumferentially to the reflector body, for example with an adhesive compound, for example with cement such as, for example, lamp cement. The adhesive compound for fastening the lamp in the neck-shaped portion, however, restricts a ventilation in the space inside the reflector body. This is why the reflector body may have a profiled, for example ribbed outer surface. This increases the surface area of the outer surface, which makes for a stronger heat transfer.
The electric element may be an incandescent body, for example in an inert gas comprising halogen, or a pair of electrodes in an ionizable gas.
An electric lamp/reflector unit is known from U.S. Pat. No. 5,387,800 in which the lamp is positioned transversely to the optical axis of the reflector. The seals of the lamp project through the reflector portion to outside the reflector. A shortening of the unit in axial direction is achieved through this orientation of the lamp in the reflector. A disadvantage of the unit is, however, that the dimension in radial direction has increased. An additional disadvantage of this unit is that the lumen output is comparatively small and that comparatively much scattering of light occurs. This is caused on the one hand by the fact that the seals of the lamp absorb and/or scatter comparatively much of the light reflected by the reflector. On the other hand, this is caused by the fact that holes are provided in the reflector portion comparatively close to the neck-shaped portion for allowing the seals to project to the exterior.